Why does rainwater pool into a shape of windshield wipers?

Question

I’m sitting in my car, it’s raining and wipers are off. However, I can clearly see how the droplets pool in a specific manner, reminiscent of wiper movements. Can someone explain the physics behind it?
Here’s how it looks like: https://ibb.co/C5M7YCL

In: Physics

Answer 1

Where there’s a bit of non-oily grime, the water can’t bead up like it normally would. Clean glass allows water to do its thing.

For eli12, it’s surface tension.

For eli14, The non-oily grime has polar molecules or ions that interact with the highly polar water that keep water from only pulling on itself, creating a surface that beads.

It’s nothing to do with polishing, btw.